Recovery of cellulose esters from scrap



Patented June 16, 1942 UNITED STATES ATENT FFICE Carl J. Malm andGustave B. Bachman, Rochester, N. Y., assignors to Eastman KodakCompany, Rochester, N. Y.,

Jersey a corporation of New No Drawing. Application March 10, 1939,Serial No. 261,102

4 Claims.

sists of an organic acid ester of cellulose. A film 5.

base is usuall overcoated or supported with a layer of material topromote the adhesion of a photo-sensitive emulsion thereto. Also, coloror tinting is employed to prevent halation. When photographic film isscrapped, it is desirable to recover the organic acid ester of cellulosewhich is used as the base of the film. To do this requires the removalof the photo-sensitive emulsion and of the subbing layer and thecoloring matter which is employed therewith. The present inventionrelates to the recovery of scrap film to which dye or color had beenapplied to prevent halation. The use of a combination of bleachingandwashing has been suggested to remove the color from film; however, bythis a.

process impurities may be introduced into the cellulose ester or thebleaching agent may deleteriously affect the organic acid ester ofcellulose. The use of leaching solvents for the removal of subbinglayers has been suggested and some of the tinting material is removedthereby. By this treatment, the removal of color is far from completed,so that up to the time of our invention, subsequent bleaching has beennecessary.

One object of our invention is to provide a method for recoveringcellulose esters from film scrap in which the color and/ or the subbinglayers ma be completely removed in one operation. Another object of ourinvention is to provide a method for film scrap recovery requiring lesstime and a less number of changes of leaching liquid than have beennecessary heretofore. Another object of our invention is to provide aprocess in which less solvent is necessary to accomplish a satisfactoryleaching than has been previously necessary.

We have found that, if the film scrap, after the emulsion has beenremoved therefrom, is treated with a leaching liquid, which willdissolve the subbing layers and remove the color but which will notdeleteriously affect the film base, containing a small amount of wettingagent, the resulting product is free of color so that a subsequentbleaching treatment is unnecessary. We have found that, by incorporatinga wetting agent, which is soluble in the leaching solvent, the leachingsolvent is much more effective to accomplish the desired purpose, asevidenced by the decreased number of changes of solvent which arenecessary and by the lessening of the time required to complete theleaching operation. By employing a wetting agent with the leachingsolvent, a film scrap can be satisfactoril leached in as little as fiveminutes, although a longer time is preferred.

Only a small amount of wetting agent need be employed in the leachingsolvent, although the presence of large amounts is not objectionable. Aslittle as .025% of wetting agent has been employed and resulted in asatisfactory product; smaller amounts can be used, such as .0l6%,however, with too small an amount of wetting agent, the results are notas satisfactory. If .016% wetting agent is incorporated in the leachingsolvent, a satisfactory product is obtained. Whereas, the film scrap,treated in accordance with our invention with only one leachingoperation, comes out nearly colorless and has a clean shiny surface whendried, the same material, which is treated in like manner in the absenceof a wetting agent, exhibits appreciable coloration and upon drying, hasan opaque surface.

To prepare the film scrap for treatment in accordance with ourinvention, the photographic gelatin emulsion is "ordinarily removed,such as by treating with hot water. After this treatment, the film scrapis subjected to the leaching treatment in which a small amount ofwetting agent is present. It is preferred that the film scrap be firstdried after the removal of the emulsion layer, as the amount of moisturepresent in the leaching solvent is thereby kept low. After the filmscrap has been agitated in the leaching solvent containing a smallamount of wetting agent, the scrap is separated from the liquid and, ifthe leaching liquid is water miscible, it maybe washed with water anddried. Often in the washing with water, considerable foaming occurs. Inthat case it is preferred that the film scrap be given a washing withleaching solvent alone subsequent to the treatment with leaching solventand wetting agent and prior to the washing with water. In this way thefoaming in the water is prevented. In this procedure the leachingsolvent employed for the second washing can, after use, be mixed with asmall amount of wetting agent and be employed for the first treatment ofanother batch of film scrap. This second leaching solvent maybe useduntil its effectiveness for preventing foaming is destroyed whereupon itmay be either used for the first leaching or, separated from theimpurities therein and re-employed for the foam preventing step.

The wetting agents, which are miscible with the leaching solvent andinert to the film base, may be employed in our invention. Some of thewetting agents, which may be used, are as follows:

1. Aliphatic or cyclo-aliphatic sulphonates or sulfates. A hydrocarbonradical in these compounds should contain ten or more carbon atoms.Other groups, which are not opposed to the conditions of operation, maybe also present. These compounds are usually obtainable either in theform of their inorganic or organic salts.

Some examples of this type of wetting agent are:

Sodium diamyl sulfosuccinate Sodium lauryl sulfate Sodium laurylsulfonate Sodium n-oleyl-n-methyl taurate 2. Non-ionic wetting agents.Examples of compounds of this type are glycerin mono-oleate, diglycololeate and glyceryl mono-steerate. As a matter of fact, a wetting agentof this type might be prepared by taking natural fat and adding glycerinthereto.

3. Cation-active wetting agents. These are compounds in which thepositive ion is large. They are usually substituted ammonium salts, suchas cetyl ammonium chloride, dimethyl benzyl ammonium chloride, laurylpyridinium ptoluene sulfonate and dimethyl benzyl cetyl ammoniumchloride. Although only compounds containing nitrogen have been listedunder this item, compounds having similar atoms instead of nitrogen,such as arsenic or phosphorus, in like chemical structures are suitablein this connection. Compounds of this type which are suitable in myinvention, where compatible with the leaching solvent are disclosed inU. S. Patent No. 2,125,031 of Polak and Weeldenburg.

4. Alkyl-substituted aromatic sulphonic acids. The compounds under thisgroup, which are suitable for use as wetting agents in our process, maybe represented by the following structural formula:

where Ar is an aromatic hydrocarbon nucleus, R is an aliphatichydrocarbon radical, X is hydrogen or an alkali metal, R" is hydrogen,OH, or OR, R being an aliphatic or aromatic hydrocarbon radical, 'n is1, 2, 3 or 4, and the total number of carbon atoms in the unit Ar(R')nis at least 11. When n is 2, 3 or 4, the aliphatic hydrocarbon radicalsrepresented by B may be the same or different. The total number ofcarbon atoms in the unit Ar-(R)n is preferably about 18 to 24.

Examples of wetting agents of this nature are keryl benzene sulfonicacid (keryl representing the mixture of hydrocarbon radicals derivedfrom kerosene) the sodium salt of which is known as Nacconol NR; kerylphenol sulfonic acid, the sodium salt of which is known as Nacconol AX;cetyl phenol sulfonic acid and p-tertiarvamyl phenol sulfonic acid.Compounds of this type, which are useful in our invention, are mentionedin Staud and Bachman application Serial No. 231,916, filed September2'7, 1938.

5. Salts of aliphatic carboxylic acids having a large number of carbonatoms such as found in ordinary soaps. Examples are: sodium palmitate,sodium stearate, triethanol ammonium laurate and diethyl ethanolammonium oleate.

In some cases in our process the addition to or presence of water in theleaching solvent cuts down the efficiency, If the dyes, which are to beremoved from the film scrap, are not water soluble or water susceptible,the presence of water renders the dyes less susceptible to the action ofthe leaching solvent; therefore, as a rule, the presence of water is tobe avoided.

The leaching solvent, which may be employed, is any organic solventwhich will remove the dye and also preferably the subbing layer, withoutany bad effect on the film base itself. The leaching solvent to beemployed will be governed to some extent by the subbing layer which isto be removed. It is also preferred, but not necessary, that theleaching liquid be water miscible, as this contributes to the facilitywith which the film scrap can be washed after the leaching. The solventmay be a mixture of methyl alcohol or some other lower aliphatic alcoholmixed with a small amount of acetone or it may be the alcohol withoutdilution, particularly if the alcohol is suitable for this purposewithout any further addition.

The following examples illustrate processes embodying our invention:

Example I 205 parts of methyl alcohol-acetone, consisting of 4 parts ofalcohol and 1 part of acetone, containing 1.6% of a Nacconol NRextractant, was agitated for 30 minutes with 50 parts of film scrap fromwhich the photographic emulsion had been removed. The methylalcohol-acetone was then drained off and the scrap was thoroughlywashed. Whereas the scrap prior to this treatment was blue, after thetreatment it was colorless and had a clean shiny surface when dried. Theused solvent, containing wetting agent, was added to a fresh 50 gramsample of scrap and agitated for 30 minutes. The scrap was then washedthoroughly and found to be substantially colorless, although it did nothave as good appearance as the film scrap obtained in the initialtreatment.

Example II 50 parts of film scrap, from which the emulsion had beenremoved, was leached with 200 parts of 4:1 alcohol-acetone containing0.1% of N-oleyl- N-methyl taurate. As in Example I, the leaching liquidwas drained from the scrap and it was then rinsed twice with 200 partsof the solvent containing no wetting agent. The scrap was then washedwith water. No foaming occurred in washing of the scrap with water as inExample I the scrap was clean, and free of color. If desired, thismethod can be performed countercurrently, such as by adding thedetergent about half way through the leaching process. Thus the freshsolvent would remove any residual wetting agent from the film scrapbefore it entered the washed water.

Example III pared favorably in appearance with the sample obtained inExample I.

Example IV The same conditions, described in Example I, were repeatedexcept that 0.167% wetting agent was employed. The film scrap, afterwashing and drying, appeared to be as good as that obtained in ExampleI.

By using a wetting agent, various other treatments, such as bleaching,which were formerly thought necessary in the recovery of scrap film,have been eliminated so that the scrap is recovered in one operation ina form suitable for directly dissolving and coating out into sheeting.The resulting sheeting, if plasticized to the same degree, hassubstantially the same properties as that of the sheeting which wasemployed to prepare the film base. Various organic acid esters ofcellulose, such as cellulose acetate, cellulose acetate propionate,cellulose acetate butyrate, cellulose propionate or cellulose butyrate,may be recovered from film scrap in which it has been employed in thefilm base in accordance with our invention.

Any organic solvent which does not dissolve the base of the film scrapbut does dissolve the dye or backing to be removed is suitable in ourprocess. Examples of the types of compounds which are suitable for useas organic solvents are:

Liquid aromatic hydrocarbons such as toluene Ethers such as di-isopropylether and the cellosolves Liquid esters such as ethyl acetate Ketonessuch as methyl ethyl ketone Lower aliphatic alcohols such as ethylalcohol and isopropyl alcohol Any liquids selected from these classeshaving the characteristics pointed out above may be em-. ployed forrecovering photographic film scrap in accordance with our invention.

We claim:

1. A method for recovering photographic film scrap having a base of alower fatty acid ester of cellulose which comprises treating scrap,which is free of gelatin emulsion, with an organic leaching solventwhich will not dissolve or deteriorate the film base, the leachingsolvent containing a small amount of a material to assist the leachingselected from the group consisting of the aliphatic and cycle-aliphaticsulphonates and sulphates in which a hydrocarbon radical thereincontains at least 10 carbon atoms, the glycols incompletely esterifiedwith higher fatty acids, the glycerols incompletely esterified withhigher fatty acids, the cation-active substituted ammonium salts, thealkyl-substituted aromatic sulphonic acids, the alkyl substitutedaromatic unit containing at least 11 carbon atoms and the alkali metaland substituted ammonium salts of the higher fatty acids.

2. A method for recovering photographic film scrap having a base of alower fatty acid ester of cellulose which comprises treating scrap,which is free of gelatin emulsion, with an organic leaching solventessentially consisting of a lower aliphatic alcohol and acetone inproportions which will not dissolve the cellulose ester but which willeffectively remove the color therefrom, the leaching solvent containinga small amount of a material to assist the leaching selected from thegroup consisting of the aliphatic and cyclo-aliphatic sulphonates andsulphates in which a hydrocarbon radical therein contains at least 10carbon atoms, the glycols incompletely esterified with higher fattyacids, the glycerols incompletely esterified with higher fatty acids,the cation-active substituted ammonium salts, the alkyl-substitutedaromatic sulphonic acids, the alkyl substituted aromatic unit containingat least 11 carbon atoms and the alkali metal and substituted ammoniumsalts of the higher fatty acids.

3. A method for recovering photographic film scrap having a base of alower fatty acid ester of cellulose which comprises treating the scrap,which is free of gelatin emulsion, with a leaching solvent essentiallyconsisting of a lower aliphatic alcohol and acetone in proportions whichwill not dissolve the cellulose ester, the leaching solvent containingthe sodium salt of keryl benzene sulphonic acid to assist the leachingoperation.

4. A method for recovering photographic film scrap having a base of alower fatty acid ester of cellulose which comprises treating the scrap,which is free of gelatin emulsion, with a leaching solvent essentiallyconsisting of a lower aliphatic alcohol and acetone in proportions whichwill not dissolve the cellulose ester, the leaching solvent containingsodium N-oleyl-N-methyl taurate.

CARL J. MALM. GUSTAVE B. BACHMAN.

